In current many years, the FCC has assigned licenses for wireless spectrum by placing it up for auction. The notion behind the auction method is that is encourages companies to roll out new providers as soon as probable to recover their investments in the licenses. In obtaining spectrum into the fingers of individuals who at first price it the most, competitive bidding also facilitates effective spectrum aggregation fairly than fragmented secondary markets.

In the past, the FCC usually relied on comparative hearings, in which the qualifications of competing candidates had been examined to award licenses in cases in which two or a lot more candidates filed applications for the very same spectrum in the exact same market place. This method was time-consuming and resource-intensive. The FCC also used lotteries to award licenses, but this created an incentive for companies to acquire licenses on a speculative foundation and resell them.

Of the three strategies of assigning spectrum, aggressive bidding has proved to be the most effective way to guarantee that licenses are assigned swiftly and to the companies that worth them the most whilst recovering the appeal of the spectrum resource for the public.1 In addition, auctions prevent the perception of the federal government making decisions that are biased toward or towards specific business players. The policies and processes of the auctions are evidently established, and the outcomes are definitive.

Auction Process

The FCC’s auctions of electromagnetic spectrum assign licenses using a exclusive methodology known as “electronic simultaneous several-spherical auctions.” This methodology is equivalent to a conventional auction, other than that as an alternative of licenses becoming offered a single at a time, a significant set of connected licenses is auctioned simultaneously and bidders can bid on any license offered.

The auction closes when all bidding exercise has stopped on all licenses. Yet another characteristic of the auction method is that it is automated. When the FCC began to design and style auctions for the airwaves, it became obvious that manual auction approaches could not adequately allocate big amounts of licenses when hundreds of interdependent licenses ended up becoming auctioned to hundreds of bidders at the identical time.

The FCC’s Automated Auction System (AAS) offers the required equipment to conduct significant auctions very effectively. The technique accommodates the needs of bidders by permitting them to bid from their offices making use of a Pc and a modem via a personal and protected wide region network (WAN). The method also can accommodate on-site bidders and telephonic bidding.

Bidders and other interested events are in a position to track the progress of the auctions via the Auction Monitoring Device (ATT), a stand-by yourself application that enables a person to track in depth info on an auction. During an auction, the FCC releases consequence files after every spherical, with particulars on all the exercise that occurred in that spherical. End users can use the ATT to import these round consequence files into a grasp database file and then see a number of various tables containing a huge quantity of info in a spreadsheet watch.

Customers can sort, filter, and query the tables to track the activity of an auction in nearly any way they desire. There are also canned tables that contains basic summary data to allow much more casual observers to track the progress of the auction in standard. The FCC also gives the capacity to plot maps of auction winners, high bidders by spherical, and much more common auction activity.

By way of a Geographic Details Technique (GIS), interested parties can use a Internet browser–based application to build queries in opposition to the database for a certain auction and have the benefits displayed in a map format. The GIS presents its query outcomes largely in maps, which the consumer can export to effortlessly transportable graphical formats. The GIS also allows the person to show info in tabular format.

At present, there are 3 queries that can be executed versus any closed or open auction in the GIS:

• Marketplace evaluation by amount of bids Makes it possible for end users to see which licenses obtained a bid in a given round and how a lot of bids each industry obtained.
• Spherical outcomes summary Provides a high-degree summary of exercise for the selected round, depicting markers for which a new substantial bid was acquired, markets for which a bid was withdrawn, and markets that had no new exercise.
• Bidder exercise Allows end users to query the database to produce a map exhibiting all the licenses for which a particular place has a substantial bid in a given round.

Organizations interested in participating in spectrum auctions need to submit an digital application to the FCC disclosing their ownership structure and identifying the markets/licenses on which they intend to bid.

Roughly two weeks after the filing deadline and 2 weeks just before the start of the auction, likely bidders should submit a refundable deposit that is utilized to purchase the bidding models necessary to area bids in the auction. This deposit is not refundable right after the auction closes. At a minimum, an applicant’s total up-front payment should be enough to create eligibility to bid on at least 1 of the licenses utilized for, or else the applicant will not be qualified to take part in the auction.

In calculating the upfront payment amount, an applicant need to figure out the optimum range of bidding units it might desire to bid on in any single round and submit a payment that covers that quantity of bidding units. Bidders have to check their calculations carefully simply because there is no provision for growing a bidder’s highest eligibility after the up-front payment deadline.

About 10 days ahead of the auction, competent bidders get their confidential bidding access codes, Automated Auction Technique computer software, telephonic bidding telephone number, and other documents needed to participate in the auction. 5 days before the commence of the auction, the FCC sponsors a mock auction that allows bidders to perform with the software, turn out to be cozy with the policies and the conduct of a simultaneous multipleround auction, and familiarize themselves with the telephonic bidding process.

When the auction commences, it continues until finally all bidding activity has stopped on all licenses. To guarantee the competitiveness and integrity of the auction procedure, the rules prohibit candidates for the identical geographic license place from communicating with every single other during the auction about bids, bidding techniques, or settlements. The winning bidders for spectrum in each industry are awarded licenses.

Within 10 organization days, each winning bidder ought to submit ample funds (in addition to its upfront payment) to provide its whole volume of cash on deposit to 20 percent of its net winning bids (actual bids a lot less any applicable bidding credits). Up-front payments are utilized first to fulfill the penalty for any withdrawn bid ahead of currently being applied toward down payments.

If a business fails to pay on time, the FCC can take back again the licenses and holds them for a potential auction. The licenses are granted for a ten-yr time period, right after which the FCC can consider them back if the holder fails to present support over that spectrum.

The FCC’s simultaneous several-spherical auction methodology and the AAS software program have created interest globally. The FCC has demonstrated the system to representatives of several nations, which includes Argentina, Brazil, Canada, Hungary, Peru, Russia, South Africa, and Vietnam. Mexico licensed the FCC’s copyrighted system and has utilized it successfully in a spectrum auction. In addition, in 1997, the FCC was awarded a bronze medal from the Smithsonian Institution for recognition of the visionary use of info technology.

The aspects of technology in the domain of networking are becoming advanced persistently with standard inventions and innovation. One of these technological inventions is Wireless Accessibility Stage that is a network capable gadget having transceiver and antenna for acquiring and sending signals from the remote clients. Typically known as WAP, this technology helps the remote consumers to get connected easily and that as well with substantial velocity via World wide web. WAP technological innovation has presented world-wide connection its real meaning.
Why you need Wireless Accessibility Level?
WAP engineering is ideal for sharing broadband World wide web connection with several pcs. This wireless sharing is meant for within the family that also functions with your current modem router but for which you require to make positive that your modem consists of either firewall NAT feature or wireless router.
Wherever set up of network cable is merely not possible, WAP rescues you here with its wireless entry to the network. For the sake of business enhancement, WAP is the greatest alternative to pick. You require Wireless Out of doors Access Points in harsh plant setting with which you can develop mesh network, point-to-level and point-to-multi point networks. You can also generate hotspots with safety separation, when you require cellular units to wirelessly entry the network.
Selection of the finest Wireless Access Point
Continual innovation in WAP Technologies by Makers has assured a high-carrying out product that serve in the very best probable method. Due to consistency in innovation, choosing the finest Wireless Access Stage is a problem. You can go by means of these beneath talked about capabilities that really should be a need to in your Wireless Access Level.
WDS Help
A ideal Wireless Accessibility Level really should help Wireless Distribution Method (WDS). It aids a wireless network to increase by employing multiple entry details that also without requiring an urge for a wired backbone to website link them. WDS allows you to produce a wireless infrastructure as the network devices turns into independent from wired LAN. With WDS feature, you can create an massive wire network by connecting a variety of wireless access points with WDS back links. It is used mostly in bigger location exactly where pulling wire is literally unattainable.
Multifunction Modes
This is a important function of WAP. The very best Wireless Access Stage ought to connect with different operational modes such as Network Bridge, Access Level, Wireless Customer Mode, and Network Bridge. When multifunctional modes are thought to be, the point require to be used treatment of is that the device is suitable with active wired network that functions effectively by basic attachment with modes by Ethernet cable to an unenclosed port in your change or router. With Wireless Ethernet Bridge Mode or Consumer mode, you can connect your notebook, Computer, printer, network digital camera to the AP machine by the aid of swap. In repeater mode, you can make addition in AP units that extend the wireless network that also with out requiring any operate backbone cables.
Technically Advanced Security Capabilities
A sophisticated Wireless Entry Factors need to be compatible with safety features like advanced wireless protection Wireless Secured Access (WPA/WPA2), SSID Broadcast Control, and MAC filter. When deployment in Corporate Network is deemed, Access Factors need to maintain technically sophisticated RADIUS authentication and wireless safety (EAP-MD5, EAP-TLS, EAP-TTLS, and PEAP), Wireless Secured Setup (WPS) that assure problems free of charge installation.
Wireless N
Presently, there is a substantial regular wireless engineering that includes the wireless 802.11n. This normal is the most superior and thus fastest wireless technology accessible in the market place. For programs like High Definition Video streaming and voice, dual-band version of each two.4 GHz and five GHz frequency bands is the ideal choice. Equipped with wireless N and MIMO technologies, the Wireless Entry Point provides longer distance coverage with the pace up to 300 Mbps or more.
About Set up of Wireless Access Stage
Largely, Wireless Entry Stage is designed and produced for indoor purposes in which the doing work setting is not constrained. There is also certain style available for outside installation acquiring rugged housing, high grade industrial components, and climatic conditions proof, rust resistant, and water-restricted enclosure. WAP designed for out of doors software can operate underneath the strenuous temperature variety of -30°C to 70°C.

Telegraphy is a form of data communication that is centered on the use of a signal code. The phrase telegraphy arrives from Greek tele meaning “distant” and graphein which means “to write”—writing at a distance. The inventor of the 1st electrical telegraph was Samuel Finley Breese Morse, an American inventor and painter.

On a trip home from Italy, Morse grew to become acquainted with the several attempts to produce usable telegraphs for long-distance telecommunications. He was fascinated by this dilemma and studied guides on physics for 2 decades to acquire the required scientific expertise.

Morse concentrated his study on the attributes of electromagnets, whereby they grew to become magnets only whilst the present flows. The intermittence of the existing created two states—magnet and no magnet—from which he developed a code for representing characters, which sooner or later grew to become identified as Morse Code. (The Worldwide Morse Code is a system of dots and dashes that can be utilized to mail messages by a flash lamp, telegraph important, or other rhythmic gadget this kind of as a tapping finger.)

His 1st attempts at building a telegraph failed, but he ultimately succeeded with the assist of some pals who have been a lot more technically knowledgeable. The signaling gadget was really basic. It consisted of a transmitter containing a battery and a important, a small buzzer as a receiver, and a pair of wires connecting the two. Later on, Morse improved it by including a 2nd switch and a 2nd buzzer to permit transmission in the opposite route as properly.

In 1837, Morse succeeded in a public demonstration of his very first telegraph. Although he acquired a patent for the system in 1838, he labored for 6 far more many years in his studio at New York University to best his invention. Eventually, on May possibly 24,1844, with a $ 30,000 grant from Congress, Morse unveiled the final results of his function. Above a line strung from Washington, D.C., to Baltimore, Morse tapped out the message, “What hath God wrought.”

The message attained Morse’s collaborator, Alfred Lewis Vail, in Baltimore, who immediately sent it back again to Morse. With the good results of the telegraph assured, the line was expanded to Philadelphia, New York, Boston, and other main cities and towns. The telegraph lines tended to adhere to the rights-of-way of railroads, and as the railroads expanded westward, the nation’s communications network expanded as effectively.

Morse Code utilizes a technique of dots and dashes that are tapped out by an operator employing a telegraph important. (It also can be employed to talk via radio and flash lamp.) Different combinations of dots and dashes signify characters, figures, and symbols separated by spaces.

Morse Code is the foundation of today’s digital communication. Though it has almost disappeared in the earth of specialist communication, it is nevertheless used in the planet of amateur radio (HAM) and is kept alive by background buffs. There are even pages on the Net that educate telegraphy and complete translations of text into Morse Code.

Wireless Telegraphy

An Italian inventor and electrical engineer, Guglielmo Marconi (1874–1937), pioneered the use of wireless telegraphy. Telegraph signals formerly had been sent through electrical wires. In experiments he conducted in 1894, Marconi demonstrated that telegraph signals also could be sent through the air.

A couple of years previously, Heinrich Hertz had made and detected the waves across his laboratory. Marconi’s achievement was in generating and detecting the waves above lengthy distances, laying the groundwork for what these days we know as radio. So-called Hertzian waves had been developed by sparks in a single circuit and detected in one more circuit a number of meters away.

By continuously refining his techniques, Marconi could quickly detect signals more than several kilometers, demonstrating that Hertzian waves could be utilized as a medium for communication. The results of these experiments led Marconi to technique the Italian Ministry of Posts and Telegraphs for permission to set up the first wireless telegraph services. He was unsuccessful, but in 1896, his cousin, Henry Jameson-Davis, organized an introduction to Nyilliam Preece, engineer-inchief of the British Article Company.

Encouraging demonstrations in London and on Salisbury Plain followed, and in 1897, Marconi obtained a patent and established the Wireless Telegraph and Signal Organization, Ltd, which opened the world’s first radio factory at Chelmsford, England, in 1898. Experiments and demonstrations continued. Queen Victoria at Osborne Residence received bulletins by radio about the health of the Prince of Wales, convalescing on the royal yacht off Cowes.

Radio transmission was pushed to better and better lengths, and by 1899, Marconi had sent a signal nine miles across the Bristol Channel and then 31 miles across the English Channel to France. Most people considered that the curvature of the earth would stop sending a signal significantly farther than 200 miles, so when Marconi was in a position to transmit across the Atlantic in 1901, it opened the door to a speedily creating wireless sector.

Industrial broadcasting was nonetheless in the future—the British Broadcasting Organization (BBC) was established in 1922—but Marconi had accomplished his purpose of turning Hertz’s laboratory demonstration into a practical indicates of communication.

By Morse’s death in 1872, the telegraph was currently being employed globally and would pave the way for the invention of the phone. Western Union had the monopoly on commercial telegraph service but spurned Alexander Graham Bell, who approached the business with an improvement that would convey voice over the very same wires.

Bell had to type his own business, American Bell Phone Company, to supply a industrial voice communication service. Given that then, voice and information technologies have progressed through separate evolutionary paths. Only in current decades has voice-data integration been pursued as a indicates of that contains the value of telecommunication services.

Software program-defined radios can be reprogrammed speedily to transmit and receive on multiple frequencies in various transmission formats. This reprogramming capability could change the way customers traditionally talk across wireless providers and promote a lot more effective use of radio spectrum.

In a software program-defined radio, capabilities that ended up formerly carried out exclusively in hardware, such as era of the transmitted radio signal and tuning of the acquired radio signal, are carried out by software program. Due to the fact these capabilities are carried out in application, the radio is programmable, permitting it to transmit and acquire above a wide array of frequencies and to emulate virtually any preferred transmission format.

The notion of application-defined radio originated with the military, wherever it was utilized speedily for electronic warfare applications. Now the cellular/wireless industries in the United States and Europe have begun work to adapt the technology to industrial communications providers in the wish of recognizing its extended-term economic benefits.

If all goes in accordance to program, future radio providers will offer seamless accessibility across cordless telephone, wireless neighborhood loop, Individual Communications Solutions (PCS), cellular mobile, and satellite modes of communication, including integrated information and paging.

Generations of Radio Methods

Very first-generation hardware-based radio techniques are created to get a particular modulation scheme. Ahandset would be constructed to work about a certain form of analog network or a certain kind of digital network. The handset worked on a single network or the other, but not both, and it could undoubtedly not cross amongst analog and digital domains. Second-era radio systems also are based in hardware.

Miniaturization allows two sets of components to be packaged into a single, compact handset. This permits the unit to operate in twin mode—for case in point, switching among Sophisticated Cell Cellphone Services (AMPS) or TDMA modulation as required. This kind of handsets are implemented making use of snap-in elements: Two current chip sets—one for AMPS and one particular for TDMA, for example—are used jointly.

Building this kind of handsets usually expenses only twenty five to fifty percent more than a single-mode handset but offers network operators and consumers far a lot more flexibility. Handsets that perform across four or a lot more modes/bands entail far far more complexity and processing strength and call for a different architecture completely. The architecture is primarily based in software and programmable digital signal processors (DSPs). This architecture is referred to as “software-defined radio” or just “software radio.”

It represents the 3rd generation of radio programs. As new technologies are positioned onto current networks and wireless requirements become a lot more fragmented—particularly in the United States—the need for a single radio unit that can operate in distinct modes and bands gets a lot more urgent. Asoftware radio handset could, for illustration, operate in a GSM-centered PCS network, a legacy AMPS network, and a potential satellite mobile network.

Operation

As noted, a computer software radio is one in which channel modulation waveforms are defined in computer software. Waveforms are produced as sampled digital signals, converted from digital to analog by means of a wideband digital-to-analog converter (DAC), and then up-converted from an intermediate frequency (IF) to the preferred radiofrequency (RF).

In related fashion, the receiver employs a wideband analog-to-digital converter (ADC) that captures all the channels of the software program radio node. The receiver then extracts, down-converts, and demodulates the channel waveform employing the software program loaded on a basic-purpose processor.

Multimode/Multiband

As competing technologies for wireless networks emerged in the early 1990s, it grew to become obvious that subscribers would have to make a choice: The more recent digital technologies presented far more sophisticated features, but protection would be spotty for some decades to come. The older analog technologies provided wider coverage but did not help the advanced characteristics. A compromise was supplied in the sort of wireless multimode/ multiband systems that offered subscribers the very best of each worlds.

At the same time, wireless multimode/multiband techniques enable operators to economically develop their networks to support new companies exactly where the desire is best. With multimode/ multiband handsets, subscribers can accessibility new digital solutions as they turn out to be obtainable whilst retaining the capability to communicate above current analog networks.

The wireless method provides users accessibility to digital channels wherever digital service is available even though providing a transparent handoff when customers roam between cells alternately served by different digital and analog technologies. As lengthy as subscribers remain within cells served by advanced digital technologies, they will keep on to appreciate the positive aspects supplied by these technologies.

When they achieve a cell that is supported by analog engineering, they will have entry only to the features supported by that technological innovation. The intelligent roaming ability of multimode/multiband programs instantly chooses the very best program for the subscriber to use at any given time. 3rd-era radio techniques are frequency-agile and extend this flexibility even even more by supporting much more modes and bands.

It is crucial to bear in mind, even so, that application radio techniques may possibly never catch up to encompass all the modes and bands that are obtainable today and that might become available in the long term. Customers will usually be confronted by selections. Creating the proper alternative will depend on calling designs, the capabilities connected with the various technologies and expectations, and the form of methods in use at international areas visited most regularly.

Multimode and multiband handsets have been available from several producers since 1995. These handsets support more than a single technology for their mode of operation and much more than one particular frequency band. An instance of a multimode wireless program is 1 that supports each AMPS and Narrowband AMPS (N-AMPS). Narrowband AMPS is a system-overlay technological innovation that delivers enhanced digital-like functions, these as Digital Messaging Services, to phones operating in a traditional analog-based mostly AMPS network.

Amid the vendors supplying twin-mode AMPS/N-AMPS handsets is Nokia, the world’s second-greatest producer of cellular phones. An instance of a multiband wireless system is 1 that supports GSM at both 900 and 1800 MHz in Europe. Between the vendors supplying twin-band GSM handsets is Motorola. The company’s Worldwide 8800 Mobile Phone makes it possible for GSM 1800 subscribers to roam on either their home or GSM 900 networks (where roaming agreements are in location) using a single cellular telephone.

Of course, handsets can be the two multimode and multiband. Ericsson, for example, provides dual-band/dual-mode handsets that support communication above each 800-MHz AMPS/Digital AMPS (D-AMPS) and 1900-MHz D-AMPS networks. Subscribers on a D-AMPS 1900 channel can hand off each to and from a D-AMPS channel on 800 MHz as well as to and from an analog AMPS channel.

Multimode and multiband wireless methods enable operators to grow their networks to help new providers in which they are necessary most, expanding to full coverage at a tempo that tends to make financial feeling. From the subscribers’ standpoint, multimode and multiband wireless systems allow them to take benefit of new digital providers that are originally deployed in significant cities while even now getting capable to talk in places served by the older analog technologies.

With its multimode capabilities, the wireless technique preferentially selects a digital channel wherever digital service is offered. If the subscriber roams out of the cell served by digital technology—from 1 served by CDMAto 1 served by AMPS, for example—a handoff occurs transparently. As lengthy as subscribers stay inside of CDMAcells, they will carry on to get pleasure from the strengths the technological innovation provides, this kind of as greater voice quality and soft handoff, which virtually eliminates dropped calls.

When subscribers get to a cell that supports only AMPS, voice top quality diminishes and the odds for dropped calls increases. However, these multimode/multiband handsets are not computer software-programmable. They depend as an alternative on packaging twin sets of hardware in the exact same handset.

Miniaturization of the numerous elements tends to make this both sensible and affordable, but this strategy has its restrictions when the amount of modes and frequencies that ought to be supported goes beyond two or a few. Beyond that level, a totally new strategy is essential that relies more on programmable components.

Regulation

Even with the promising concept of application-defined radios, the rollout of customer goods that use the engineering has been sluggish. In September 2001, the FCC adopted rule adjustments to accommodate the authorization and deployment of computer software-defined radios. Beneath the past guidelines, if a producer needed to make modifications to the frequency, electrical power, or sort of modulation for an approved transmitter, a new approval was needed, and the equipment had to be relabeled with a new identification amount.

Simply because software program-defined radios have the capacity of becoming reprogrammed in the discipline, these demands could be overly burdensome and hinder the deployment of computer software-defined radios to buyers. Below the new principles, software program modifications in a software-defined radio can be manufactured by way of a “permissive change” that has a streamlined filing process.

The FCC identification number will not have to be transformed, so products in the area will not have to be relabeled. These permissive changes can be obtained only by the unique grantee of the gear authorization. To allow for changes to products by other parties this sort of as software program developers, the FCC will permit an optional “electronic label” for software-defined radios, in which the FCC identification amount could be shown on a liquid-crystal display (LCD) or related screen.

It will let yet another get together to obtain an gear approval in its title and become the party responsible for compliance rather of the authentic grantee. The FCC also requires that a grantee get adequate steps to avert unauthorized software program modifications to radios, but it declined to set distinct protection specifications at this time. This will permit makers flexibility to produce innovative equipment while at the very same time present for oversight of the adequacy of this kind of actions by means of the equipment authorization procedure.

Application radio architectures not only decrease the complexity and expense of serving a various customer base, they also simplify the integration and management of rapidly emerging standards. With computer software-based radio programs, access points, cell sites, and wireless info network hubs can be reprogrammed to meet shifting standards requirements as a substitute of replacing them or preserving them in parallel with a newer infrastructure.

From the standpoint of customers, the exact same hardware would carry on to be used—only the application will get upgraded. This could signal the end of outdated mobile telephones. Buyers will be capable to upgrade their phones with new applications—much as they would purchase new plans to add new capabilities to their computer systems. Even though the positive aspects are obvious, business application-defined radio methods are nevertheless a number of decades away. Till they grow to be available, users will have to make do with the current generation of multimode/multiband handsets.

In the years that followed the publishing of the original 802.11 standard, new task groups were assembled to address potential enhancements to the standard. So far, nine amendments to the standard have been ratified and published by the distinctive task groups. These ratified supplements will now be discussed in a somewhat chronological order.

802.11b Amendment

Although Wi-Fi consumer market continues to grow at a tremendous rate, 802.11b compatible WLAN equipment gave the industry the first needed huge shot in the arm. In 1999, the IEEE Task Group b (TGb) published the IEEE Std.

802.11b-1999, and it was later amended and corrected as IEEE Std. 802.11b-1999/Cor1-2001. The Physical layer medium that is defined by 802.11b is strictly direct sequence spread spectrum (DSSS).

The frequency space in which 802.11b radio cards can operate is the unlicensed 2.4 to 2.4835 GHz ISM band. The TGb Task Group’s main goal was to achieve higher data rates within the 2.4 GHz ISM band.

802.11b radio cards accomplish this feat by using a different spreading/coding technique called Complementary Code Keying (CCK) and modulation methods using the phase properties of the RF signal. 802.11 cards used a spreading technique called the Barker Code .

The end result is that 802.11b radio cards support data rates of 1, 2, 5.5 and 11 Mbps. 802.11b systems are backward compatible with the 802.11 DSSS data rates of 1 Mbps and 2 Mbps.

The transmission data rates of 5.5 and 11 Mbps are known as High-Rate DSSS (HR-DSSS) . Once again, understand that the supported data rates refer to available bandwidth and not aggregate throughput.

802.11a Amendment

During the same year the 802.11b amendment was approved, another very important amendment was also ratified and published as IEEE Std. 802.11a-1999.

The engineers in the TGa Task Group set out to define how 802.11 technologies would operate in the newly allocated Unlicensed National Information Infrastructure (UNII) frequency bands.

802.11a radio cards can transmit in three different 100 MHz unlicensed frequency bands in the 5 GHz range, as shown in list below. The 2.4 GHz ISM band is a much more crowded frequency space than the 5 GHz UNII bands.

Microwave ovens, Bluetooth, cordless phones, and numerous other devices all operate in the 2.4 GHz ISM band and are potential sources of interference.

• UNII-1 (lower) – 5.150 GHz – 5.250 GHz
• UNII-2 (middle) – 5.250 GHz – 5.350 GHz
• UNII-3 (upper) – 5.725 GHz – 5.825 GHz

In addition, the sheer number of 2.4 GHz WLAN deployments has often been a problem in environments such as multitenant office buildings. One big advantage of using 802.11a WLAN equipment is that it operates in the less crowded 5 GHz UNII bands.

Eventually the three UNII bands will also become crowded. Regulatory bodies such as the FCC are opening up more frequency space in the 5 GHz range. 802.11a radio cards operating in the 5 GHz UNII bands are classified as clause 17 devices.

As defined by the 802.11a amendment, these devices are required to support data rates of 6, 12, and 24 Mbps with a maximum of 54 Mbps. With the use of a spread spectrum technology called Orthogonal Frequency Division Multiplexing (OFDM) , data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps are supported in most manufacturers’ radio cards.

It should be noted that an 802.11a radio does not have to support all of these rates and a vendor may have a different implementation of data rates that is not compatible with another vendor.

It should also be noted that 802.11a radio cards cannot communicate with 802.11 or 802.11b radio cards for two reasons. First, 802.11a radio cards use a different spread spectrum technology than 802.11/802.11b devices. Second, 802.11a devices transmit in the 5 GHz UNII bands, while the 802.11/802.11b cards operate in the 2.4 GHz ISM band.

The good news is that 802.11a can coexist with 802.11 or 802.11b/g cards in the same physical space because these cards transmit in separate frequency ranges. In Figure below, you see an access point (AP) with both a 2.4 GHz 802.11b/g radio and a 5 GHz 802.11a radio.

Many enterprise wireless deployments run both 802.11a and 802.11b/g networks simultaneously.

802.11g

Another amendment that generated a lot of excitement in the Wi-Fi marketplace was published as IEEE Std. 802.11g-2003. The IEEE defines 802.11g cards as clause 19 devices, which transmit in the 2.4 to 2.4835 GHz ISM frequency band.

The main goal of the TGg Task Group was to enhance the 802.11b Physical layer to achieve greater bandwidth yet remain compatible with the 802.11 MAC. To achieve the higher data rates, Extended Rate Physical OFDM (ERP-OFDM) technology is used exactly as defined in the 802.11a amendment.

Therefore, data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps are possible using OFDM technology, although once again the IEEE only requires the data rates of 6, 12, and 24 Mbps. To maintain backward compatibility, the DSSS data rates of 1, 2, 5.5, and 11 are supported as well.

The 802.11g amendment defines the use of several PHYs but requires support for both DSSS and ERP-OFDM. The good news is that an 802.11g AP can communicate with 802.11g client stations as well as 802.11b stations.

The ratification of the 802.11g amendment triggered monumental sales of Wi-Fi gear in both the small office, home office (SOHO) and enterprise markets because of both the higher data rates and the backward compatibility with older equipment.

Spread spectrum technologies cannot communicate with each other, yet the 802.11g amendment mandates support for both DSSS and ERP-OFDM. In other words, ERP-OFDM and DSSS technologies can coexist, yet they cannot speak to each other.

Therefore, the 802.11g amendment calls out for a protection mechanism that allows the two technologies to coexist. The goal of the 802.11g “protection mechanism” is to prevent ERP-OFDM radio cards from transmitting at the same time as DSSS radio cards.

The 802.11g amendment also specifies other optional technologies, including Packet Binary Convolutional Coding (PBCC). This technology is optional and is rarely used.

802.11d

The original 802.11 standard was written for compliance with the regulatory domains of the United States, Canada, and Europe. Regulations in other countries might define different limits on allowed frequencies and transmit power.

The 802.11d amendment, which was published as IEEE Std. 802.11d-2001, added requirements and definitions necessary to allow 802.11 WLAN equipment to operate in areas not served by the original standard.

Country code information is delivered in fields inside two wireless frames called beacons and probe requests. This information is then used by 802.11d compliant devices to ensure that they are abiding by a particular country’s frequency and power rules.

The 802.11d amendment also defines other information specific to configuration parameters of a Frequency Hopping (FHSS) access point. FHSS parameters such as hopping patterns might vary from country to country, and the information needs to be once again delivered via the beacon or probe response frames.

This information would only be useful in legacy deployments using FHSS spread spectrum technology.

802.11F

The IEEE Task Group F (TGF) published IEEE Std. 802.11F-2003 as a recommended practice in 2003. The original published 802.11 standard mandated that vendor access points support roaming.

A mechanism is needed to allow client stations that are already communicating through one access point to be able to jump from the coverage area of the original AP and continue communications through a new access point.

A perfect analogy is the roaming that occurs when using a cellular telephone. When you are talking to your best friend on the cell phone while driving in your car, your telephone will roam between cellular towers to allow for seamless communications and hopefully an uninterrupted conversation.

Seamless roaming allows for mobility, which is the heart and soul of true wireless networking and connectivity. In Figure below, you see a station downloading a file through AP-1 from an FTP server residing on a wired network backbone. Please note that the access points have overlapping areas of coverage.

As the station moves closer to AP-2, which has a stronger signal, the station may roam to access point 2 and continue the FTP transfer through the portal supplied by the new access point.

Although the handover that occurs during roaming can be measured in milliseconds, data packets intended for delivery to the station that has roamed to a new access point might still be buffered at the original access point.

In order for the buffered data packets to find their way to the station, two things must happen:

1. The new access point must inform the original access point about the station that has roamed and request any buffered packets.
2. The original access point must forward the buffered packets to the new access point via the distribution system for delivery to the client who has roamed.

Figure below illustrates these two needed tasks.

Although the original 802.11 standard calls for the support of roaming, it fails to dictate how roaming should actually transpire. The IEEE initially intended for vendors to have flexibility with implementing proprietary AP-to-AP roaming mechanisms.

The 802.11F amendment was an attempt to standardize how roaming mechanisms work behind the scene on the distribution system medium, which is typically an 802.3 Ethernet network using TCP/IP networking protocols. 802.11F addresses “vendor interoperability” for AP-to-AP roaming.

The final result was a recommended practice to use the Inter Access Point Protocol (IAPP). The IAPP protocol uses announcement and handover processes that result in how APs inform other APs about roamed clients as well as define a method of delivery for buffered packets.

802.11h

Published as IEEE Std. 802.11h-2003, this amendment defines mechanisms for dynamic frequency selection (DFS) and transmit power control (TPC) that may be used to satisfy regulatory requirements for operation in the 5 GHz band in Europe. DFS is used for spectrum management of 5 GHz channels for 802.11a radio cards.

The European Radiocommunications Committee (ERC) mandates that radio cards operating in the 5 GHz band implement a mechanism to avoid interference with radar systems as well as provide equable use of the channels. The DFS service is used to meet the ERC regulatory requirements.

The dynamic frequency selection (DFS) service provides for the following:

• An AP will allow client stations to associate based on the supported channel of the access point. The term associate means that a station has become a member of the AP’s wireless network.

• An AP can quiet a channel to test for the presence of radar.

• An AP may test a channel for the presence of radar before using the channel.

• An AP can detect radar on the current channel and other channels.

• An AP can cease operations after radar detection to avoid interference.

• When interference is detected, the AP may choose a different channel to transmit on and inform all the associated stations.

TPC is used to regulate the power levels used by 802.11a radio cards. The ERC mandates that radio cards operating in the 5 GHz band use TPC to abide by a maximum regulatory transmit power and are able to alleviate transmission power to avoid interference.

The TPC service is used to meet the ERC regulatory requirements. The transmit power control (TPC) service provides for the following:

• Stations can associate with an AP based on their transmit power.
• Designation of the maximum transmit power levels permitted on a channel as permitted by a regulations.
• An AP can specify the transmit power of any or all stations that are associated with the access point.
• An AP can change transmission power on stations based on factors of the physical RF environment such as path loss.

The information used by both DFS and TPC is exchanged between stations and access points inside of management frames. Although the 802.11h amendment was ratified specially to address compliance with European regulations in the 5 GHz band, many vendors have also applied TPC and DFS-like services to radio cards operating in the 2.4 GHz ISM band.

802.11i

From 1997 to the year 2004, there really was not much defined in regard to security in the 802.11 standard. Two key components of any wireless security solution are data privacy (encryption) and authentication (identity verification).

For seven years, the only defined method of encryption in an 802.11 network was the use of 64-bit static encryption called Wired Equivalent Privacy (WEP).

WEP encryption has long been cracked and is not considered to be an acceptable means of providing data privacy. The 802.11 standard defined two methods of authentication. The default method is Open System authentication, which verifies the identity of everyone regardless.

Another defined method is called Shared Key authentication, which opens up a whole new can of worms and potential security risk. The 802.11i amendment, which was ratified and published as IEEE Std. 802.11i-2004, has finally defined stronger encryption and better authentication methods.

The intended goal was to better hide the data flying through the air while at the same time place a bigger guard at the front door. The 802.11i security amendment is without a doubt one of the most important enhancements to the original 802.11 standard due to the seriousness of properly protecting a wireless network.

The major security enhancements addressed in 802.11i are as follows: Data privacy Confidentiality needs have been addressed in 802.11i with the use of a stronger encryption method call Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (CCMP), which uses the Advanced Encryption Standard (AES) algorithm.

The encryption method is often abbreviated as CCMP/AES, AES CCMP, or often just CCMP. The 802.11i supplement also defines an optional encryption method known as Temporal Key Integrity Protocol (TKIP), which uses the RC-4 stream cipher algorithm and is basically an enhancement of WEP encryption.

Authentication 802.11i defines two methods of authentication using either an IEEE 802.1X authorization framework or preshared keys (PSKs). An 802.1X solution requires the use of an Extensible Authentication Protocol (EAP), although the 802.11i amendment does not specify what EAP method to use.

Robust Security Network (RSN) This is a method of establishing authentication, negotiating security associations, and dynamically generating encryption keys for clients and access points.

The Wi-Fi Alliance also has a certification known as Wi-Fi Protected Access (WPA2), which is a mirror of the IEEE 802.11i security amendment. WPA version 1 was considered a preview of 802.11i and WPA version 2 is fully compliant with 802.11i.

The Wi-Fi Alliance also has a certification known as Wi-Fi Protected Access (WPA2), which is a mirror of the IEEE 802.11i security amendment. WPA version 1 was considered a preview of 802.11i and WPA version 2 is fully compliant with 802.11i.

802.11j

The main goal set out by the IEEE Task Group j (TGj) was to obtain Japanese regulatory approval by enhancing the 802.11 MAC and 802.11a PHY to additionally operate in Japanese 4.9 GHz and 5 GHz bands. The 802.11j amendment was approved and published as IEEE Std. 802.11j-2004.

In Japan, 802.11a radio cards can transmit in the lower UNII band at 5.15 GHz to 5.25 GHz as well as a Japanese licensed/unlicensed frequency space of 4.9 GHz to 5.091 GHz. 802.11a radio cards use OFDM technology with required channel spacing of 20 MHz.

When 20 MHz channel spacing is used, data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps are possible using OFDM technology. Japan also has the option of using OFDM channel spacing of 10 MHz, which results in available bandwidth data rates of 3, 4.5, 6, 9, 12, 18, 24, and 27 Mbps.

The data rates of 3, 6, and 12 Mbps are mandatory when using 10 MHz channel spacing.

802.11e

Since the adoption of the original 802.11 standard, there has not been any adequate quality of service (QoS) procedures defined for the use of time-sensitive applications like Voice over IP (VoIP). Voice over Wireless IP (VoWIP) is also known as Voice over Wirless Lan (VoWLAN) and as Voice over Wi-Fi (VoWiFi).

Although deployments so exist, the QoS capabilities are typically handled at upper layers using proprietary solutions. Application traffic such as voice, audio, and video has a lower tolerance for latency and jitter and requires priority before data traffic.

The newly approved IEEE Std. 802.11e-2005 amendment defines the layer 2 MAC methods needed to meet the QoS requirements for time-sensitive applications over IEEE 802.11 wireless LANs. The original 802.11 standard defined two methods in which an 802.11 radio card may gain control of the half-duplex medium.

The default method, Distributed Coordination Function (DCF), is a completely random method of who gets to transmit on the wireless medium next. The original standard also defines another medium access control method called Point Coordination Function (PCF), where the access point briefly takes control of the medium and polls the clients.

The 802.11e amendment defines enhanced medium access methods to support QoS requirements. Hybrid Coordination Function (HCF) is an additional coordination function that is applied in an 802.11e QoS wireless network. HCF has two access mechanisms to provide QoS.

Enhanced Distributed Channel Access (EDCA) is an extension to DCF. The EDCA medium access method will provide for the “prioritization of frames” based on upper-layer protocols.

Application traffic such as voice or video will be transmitted in a timely fashion on the 802.11 wireless medium, meeting the necessary latency requirements.

Hybrid Coordination Function Controlled Access (HCCA) is an extension to PCF. HCF gives the access point the ability to provide for “prioritization of stations.” In other words, certain client stations will be given a chance to transmit before others.

The Wi-Fi Alliance also has a certification known as Wi-Fi Multimedia (WMM). The WMM standard is a “mirror” of 802.11e and defines traffic prioritization in four access categories with varying degrees of importance.